Process for winding a yarn package

ABSTRACT

A process for winding yarn into a cylindrical-bodied substantially straight-ended package wherein the yarn is traverse wound in layers of helical coils on a bobbin and the helix angles of the coils are cyclically varied from a minimum to a maximum and back to a minimum value during a spaced periodic excursion by periodically increasing the traverse rate to a value above that used for ribbon breaking. The maximum value of the helix angle in the excursion is greater than the maximum positive value used in the ribbon-breaking portion of the cycle. Thread line tension variations due to these wide variations in helix angles may be compensated for by periodically decreasing the rate of peripheral package winding speed coincidently with and proportional to the periodic increases in traverse rate.

I United States Patent [151 3,638,872

Jennings 1 Feb. 1, 1972 [54] PROCESS FOR WINDING A YARN 2,509,250 5/1950Roberts ..242/4S PACKAGE 3,228,617 l/l966 Roberts ...242/45 3,412,94911/1968 Polese ..242/45 [72] Inventor: Uel Duane Jennings, SignalMountain,

Tenn- Primary Examiner-Stanley N. Gilreath [73] Assignee: E. I. du Pontde Nemours and Company, Emmme"wemer Schroeder Wilmington, Del.Attorney-Howard P. West, Jr.

[22] Filed: Mar. 28, 1968 [57] ABSTRACT [21] PP N0; 716,731 A processfor winding yarn into a cylindrical-bodied substantially straight-endedpackage wherein the yarn is traverse [52] U 5 Cl 242/18 I wound inlayers of helical coils on a bobbin and the helix an- [511 1". .Cl 54/58g of the cons am cyclically varied from a minimum to a [58] Fie'ld242/18 188C 'i l8 1 maximum and back to a minimum value during a spacedperiodic excursion by periodically increasing the traverse rate 242/43 l57/94 to a value above that used for ribbon breaking. The maximum I 56]References Cited value of the helix angle in the excursion is greaterthan the maximum positive value used in the ribbon-breaking portionUNITED STATES PATENTS of the cycle. Thread line tension variations dueto these wide variations in helix angles may be compensated for byperiodi- 2,608,354 8/ 1952 Whittaker ..242/43 Cally decreasing 3 rate ofperipheral package winding speed 2,649,254 8/1953 Balthrop, .lr...242/43 coincidenfly with and proportional to the periodic incl-easesin 3,241,779 3/1966 Bray et a1 ...242/18.1 traverse ram 3,310,248 3/1967Have ..242/43 3,402,898 9/1968 Mattingly ..242/18.1 X 1 Claims, 12Drawing Figures PATENTEUFEB H972 3,638,872 MET 30? 3 PROCESS FOR WINDINGA YARN PACKAGE BACKGROUND OF THE INVENTION This invention relates to thecrosswinding of yarns and more particularly to the winding of yarnpackages with improved formation and stability.

It is desirable for economic reasons to wind large packages of yarn athigh-thread line speeds. A cylindrical flat-ended package is preferredbecause more pounds of yarn can be wound in a given package diameter.Such packages are commonly formed by windups employing a surface drive.The drive roll is operated at a constant speed thus maintaining aconstant surface velocity of the driven package despite the growth ofthe package as the filamentous material is wound thereon. A cam-actuatedreciprocating traverse guide may be used to lay the yarn onto the bobbinin layers of helical coils either directly or by means of a print roll.

Currently used high-speed, i.e., l,500 y.p.m. or higher, windingtechniques do not give satisfactory package formation seriously limitingthe size of packages wound. Attempts to achieve increased package sizeor higher windup speeds are accompanied by an increase in packagedefects. Major defects detracting from good package aesthetics includebulge, spiral fans, overthrown ends, and high shoulders. All of theseappear to be related in some way to yarn laydown at the reversals, i.e.,the points at which the yarn changes direction at the ends of acylindrical straight-ended package.

Heretofore, means have been devised to improve yarn distribution at andnear the package ends, such as by superimposing an axial reciprocationon the primary traverse stroke or by changing the length of the strokecyclically by mechanical means with essentially no change in yarn helixangle to spread out or disperse the yarn laydown at the package ends orshoulders. These and other approaches provide very limited dispersionpattern or because of mechanical limitations are not applicable tohigh-winding speeds.

It is also a common practice in crosswinding to vary traverse speeds ina regular cycled fashion between a positive value and a negative valueabout a predetermined traversal rate for the purpose of preventingribbons, which are a buildup of superimposed yarn windings laidapproximately one on top of the other. These speed fluctuations howeverare relatively small and have little effect on the yarn laydown patternat the reversals.

It is known that increases in traverse rate, that is, winding at largerhelix angles may be used to reduce package bulge and move the yarnreversals on the package inward. However, the use of high-helix anglesper se is restricted by the problem of overthrown ends. It is also knownthat overthrown ends can be reduced by slower, more stable reversals atthe end of the traverse stroke, but this leads to excessively high andhard shoulders on the package. No completely satisfactory balance ofconditions for high-speed winding exists with the currently knownwinding concepts.

SUMMARY OF THE INVENTION It is a primary object of this invention toprovide a method of winding which produces substantial improvements inpackage formation. Another object of this invention is to provide ayarn-winding process adapted to produce large yarn packages withimproved stability in handling and shipping. Another object is toprovide a method of controlling yarn tensions in winding. A furtherobject is to provide improved packages of yarn wound under high tension.A further object is to provide yarn packages with low variations insurface hardness.

These and other desirable objectives are accomplished in a process forwinding yarn into a cylindrical-bodied substantially straight-ended yarnpackage wherein the yarn is forwarded at an essentially constant threadline speed and is wound on a bobbin in layers of helical coils at asubstantially constant helix angle to form the package. During winding,the package is rotated at a substantially constant peripheral rate ofspeed while the yarn is traversed back and forth axially across thepackage at a substantially constant traversal rate. According to theinvention, the improvement comprises increasing the traversal rate inspaced repeating periods throughout the winding of the package. Thelinear speed of traversing is regulated in a predetermined pattern overshortspaced repeating periods greater than the period of one traversecycle such that the helix angle is held substantially constant then isvaried cyclically to a helix angle significantly larger than the maximumhelix angle attained during the period of winding at substantiallyconstant helix angle. Tension fluctuations in the winding yarn caused bycyclically varying the helix angle may be compensated for by varying theperipheral package winding speed coincident with and in an inverserelationship with respect to the traverse speed.

According to another aspect, the invention comprises acylindrical-bodied substantially straight-ended yarn package wound on abobbin in layers of helical coils characterized by the helix angle ofthe coils in the package being varied in spaced repeating periodsthroughout the package from a minimum value to a maximum value and backto the minimum value in each period. The helix angle of the coils isvaried cyclically in spaced periods throughout the package from a basehelix angle through a range of helix angles such that the maximum helixangle is substantially larger than the maximum positive helix angle inthe intervening base periods, and the point at which the yarn reversesdirection at or near the end of the package in a helical coil isdisplaced axially inward from the end of the package in directrelationship to the helix angle in that helical coil.

In the subject method of winding a yarn into a package the yarn laydownat the reversal points is dispersed inward away from the package endsduring the period of changing helix or excursion because, with no changebeing made in the actual length of the transverse stroke, the effectivestroke length is reduced when yarn at essentially constant thread linespeed is laid down at higher helix angles and then increased when yarnis again laid down at lower helix angles. Using the variablehelixwinding method of the invention, overthrown ends are not obtained at thehigher helix angles because the package ends or walls are defined by theyarn laid down during the period of low-helix traversing. The minimum orbase angle in the helix angle cycle is generally selected to be at ornear the optimum angle which would be selected for good winding atessentially constant helix angle with particular regard to minimizingoverthrown ends. Higher maximum helix angles can be tolerated and thushigher average helix angles can be obtained because winding at theminimum or base angle establishes the package walls.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of the yarnbeing wound into a cylindrical crosswound package.

FIG. 2 is a block diagram of a control system used to vary the traverseand winding speeds according to the invention.

FIG. 3 is a graph of helix angle vs. time for an embodiment of theinvention.

FIG. 4 is an enlarged portion of the graph of FIG. 3 showingribbon-breaking cycle added.

FIGS. 5 and 7 are end and front views of a package illustrating packagedefects encountered in prior art winding.

FIG. 6 is a schematic illustration of a yarn laydown pattern at thereversal showing a substantially constant helix angle as used in priorart winding.

FIG. 8 is a schematic illustration of yarn laydown according to theinvention; single traverse strokes of highand low-helix angles areshown, as well as the final package buildup.

FIG. 9 is a schematic illustration of yarn laydown pattern at one end ofa package according to the invention.

FIGS. 10 and 11 are graphs of helix angle vs. time representing helixangle cycles which may be used in practice of the invention.

FIG. 12 is a graph of change in helix angle vs. core bulge for 3 anembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED I EMBODIMENT Referring to FIG. Iit will be seen that the windup chosen for purposes of illustrationgenerally includes, as components thereof, a traverse cam 20, a surfacedrive roll 14, swing arm 28 mounted for relative rotation about pivot 30and rotatably supporting bobbin 16, a reciprocating traverse guide 12through which yarn from a source (not shown) advances from guide 11under drive roll 14 to a package 18 on bobbin 16. Suitable means such asmotors 22, 24 along with belts 26, 26 are used to drive traverse cam anddrive roll 14 respectively.

Motors 22, 24 are synchronous motors and their speeds are individuallycontrolled by solid-state power supplies 32, 34 connected to the motorsthrough leads 36, 38. These power supplies vary motor speed by varyingthe frequency of the voltage supplied to the motors. A functiongenerator 40 is connected to power supplies 32, 34 through leads 42, 44respectively.

Referring now to FIG. 2 function generator 40 is seen to include signalgenerators 50, 52 connected to a coupler 54, which combines the signals51, 53 generated by generators 50, 52 into a single waveform 55 which inturn is fed to amplifier 56, and inverter 58. Amplifier 56 amplifiessignal 55 to form signal 55 which is fed over lead 42 to solid-statepower supply 32. Inverter 58 inverts signal 55 to form signal 59 whichis then amplified as desired in amplifier 60 to signal 59' that is fedover lead 44 to solid-state power supply 34. Signals 55 and 59' serve tomodify the output voltage frequency of power supplies 32, 34 and therotational speeds of motors 22, 24 are changed accordingly. Theresultant speed changes vary the traversing rate and consequently thepackage helix angle and the peripheral package speed in a predeterminedpattern in accordance with the output of function generator 40. The yarnpackage 18 is driven at a peripheral speed, varied in accordance withthe inverted output signal 59', by contact with drive roll 14 which actsalso as a print roll in forwarding to the package 18 the yarn laid downfrom traverse guide 12. As yarn builds on package 18, spring-loadedpivot arm 28 is urged away from the surface of roll 14 to permit theincrease in package diameter. Throughout the course of winding the helixangle at which the yarn is laid on the package 18 is varied cyclicallyby controlling the rate of the traverse guide 12. The throw of thetraverse guide, i.e., the distance that the guide 12 moves, is notchanged. The length of the yarn laydown pattern is afi'ected by changingthe angle at which the yarn is laid down. It will also be realized that,the extent of change in length of the pattern on the yarn package willdepend on part on yarn friction and retraction properties, and on rollsurface friction.

FIG. 8 shows schematically a single yarn coil 21, traversed at low-helixangle 31 and a second single yarn coil traversed at a higher helix angle33. The change in laydown length (37 vs. 39) is related to the yarn lagexisting between the traverse guide motion and the yarn laydown on theprint roll or package, and on yarn reversal slippage on the print rollor package.

Other winding parameters being held constant, the laydown pattern isshortest at the larger helix angle 33 and longest at the smallest helixangle 31. This means that the package ends 19 are defined as the yarn iswound at lowest helix angle 31 in the helix angle cycle. The helix anglecycle is the cycle of helix angle vs. time (FIGS. 3, 4, 10, 11) and isnot to be confused with the cycling of the traverse guide in one backand forth displacement of the yarn across the bobbin and herein referredto as the transverse cycle. Helix angles will be understood to be theangles measured at the package surface between the yarn coils 21, 25 anda plane perpendicular to the package axis away from the package end 19.

As shown schematically in FIG. 9, coils 21, 23, 25 laid down atdifferent angles will show a disperse pattern (i.e., dispersion) at andnear the package end 19. This area will be called the package shoulder.The reversal 21a of coil 21 at lowest helix angle defines the packageend 19 The reversal 23a of coil 23 wound at a higher helix angle isdisplaced inward slightly toward the center of the package and thereversal 25a of coil 25 wound at the maximum helix angle is displacedinward a maximum distance indicated by dotted line 35'. In periods ofwinding at changing helix angles, recurring disperse pattern isattained. This pattern from the beginning to the end of a period ofchanging helix angles may be compared with that produced by aconventional winding shown in FIG. 6 in which the reversals 15 of allthe coils 17 with a constant helix angle 13 are laid down essentially atthe package end 19. In practice in such a laydown pattern, more yarn islaid at the package end or edge than elsewhere because the reversals arenot instantaneous and package defects associated with prior art windingare developed.

FIGS. 5, 7 illustrate the defects that are encountered using prior artwinding techniques. For example, package 18' includes bulging 2, highshoulders 3, spiral fans '7 and overthrown ends 8. Also illustrated arethe accompanying defects of dish 5, dip 4, and telescoping 6. However,telescoping is most likely to occur during package shipment rather thanduring the winding of the package.

To overcome these defects, a cycle incorporating changing helix anglesis selected to provide regulated yarn laydown at the package shoulder. Ahelix angle cycle used in a preferred embodiment of the invention isdisplayed in FIG. 3 showing equal accelerating and decelerating ratechanges of helix angle during time period A spaced by a time period C oftraversing at essentially constant helix angle. This latter period isnecessary to achieve adequate firmness at the package shoulder.Accelerating and decelerating rate changes as shown in FIG. 10 (70') mayalso be used. By the period, C, of winding at substantially constanthelix angle is meant that period during which either no change intraverse rate is made or relatively small changes between a positivevalue and a negative value about a predetermined traverse rate commonlyused for ribbon breaking, may be made. The latter is a period duringwhich the speed of traversing over several seconds varies only a smallpercentage from the average speed in that period. Such a period isindicated in FIG. 4 as including a regularly cycled variation 72, whichis a typical cycle in which a ribbon making motion (usually about i 2 or3 percent around the mean traverse rate) is imposed during the constanthelix period of the cycle. The ratio (A/C) of the time period ofchanging helix angle 70 to the time period of essentially constant helixwinding C (in FIG. 3) is preferably in the range of from one-seventh tothree-seconds.

In the preferred winding process the ribbon breaking cycles areperiodically interrupted by excursions in helix angle (70, FIG. 4) whosemaximum value is greater than the maximum positive value used in theribbon breaking portion of the cycle. While as stated above that usuallyribbon breaking cycles are about azt2 or 3 percent variation it shouldbe understood that larger variations in ribbon breaking may be madeproviding the largest helix angle reached in ribbon breaking does notexceed the value at which yarn slippage at the reversals is incipientfor a particular set of winding conditions and beyond which continuedoperation is impossible because of instability and collapse of thepackage shoulder.* (*An excursion in helix angle is any change whichexceeds that magnitude at which slippage is incipient.) In addition, therate of change of helix angle in degrees per second in both excursionsand ribbon breaking such as illustrated in periods A and C respectivelyin FIG. 4 should be of sufficient magnitude to separate suc cessivewraps (helical coils) by at least one splay width, i.e., thecenterline-to-centerline distance between successive wraps should atleast equal the width of a yarn bundle when wrapped under windingtension around a cylindrical surface of minimum package diameter.

The period C between excursions of rapidly changing helix angle need notbe at a constant average angle but may be increased slightly ordecreasing slightly as indicated in FIG. 11. Additionally, successiveperiods C need not be of constant length, i.e., equispaced nor does thepeak angle reached need to remain constant throughout package winding.

The relatively large changes in helix angle required to achievedispersion lead to small changes in thread line speed, and consequentfluctuations in thread line tension. To eliminate these fluctuations andachieve uniform tension in winding, small compensating changes are madein drive roll speed coinciding with the time at which changes are madein traverse rate. In the usual case these drive roll speed changes asthe maximum helix angle is reached, are on the order of about 2 percentof the average winding speed during the period of winding at constanthelix angle. As helix angle increases, thus tending to increase yarnthread line speed, drive roll speed is reduced in unison to counteractthe speed change and thus to keep thread line tension relativelyconstant in spite of the changing helix angle. Tension control leads tothe desired dyeing uniformity in the yarn.

By varying the helix angle cyclically throughout the package, a higheraverage helix angle obtained from the variable helix period provides amore stable package structure to resist bulge of the package. When thehelix angle of the yarn is greater, the yarn can more easily preventaxial movement in the yarn coil. At the same time dispersion of yarnlaydown at the reversals is obtained with the result that packagedensity at the shoulders is regulated and the package defects occurringin prior art winding associated with yarn laydown at the reversals arelargely eliminated. Thus, substantially any size package with minimumdefects may be wound. Variable helix winding is particularlyadvantageous at high winding speeds. It is not dependent on theoperation of complex mechanical devices subject to inordinate wear orbreakdown.

In a preferred embodiment, the helix angle of winding is about 1 10percent above the base angle for good constant helix winding generallybegin to build a circumferential n'dge inboard of each shoulder,however, resulting packages are still much improved compared to priorart packages.

The shape of the cyclic pattern of changes in helix angle will 'bedetermined by the type of package characteristics desired.

The shape of the cycle curve shown in FIGS. 3, 4 while desirable forsome packages will not necessarily be optimum for all packages. Theshape and the amplitude of the variable helix portion of the helix anglevs. time curve and the relationship of period A to the period C can varyover wide limits without de' parting from the spirit of this invention.

EXAMPLE I A continuous filament nylon yam of 40 denier and I3 filamentsis wound up at a nominal thread line speed of 3,000 y.p.m. into 4-poundpackages 7 inches long. The speed of the traverse guide is varied over aperiod of l3 seconds and is then held relatively constant for a periodof 19 seconds, the complete helix angle cycle being repeated each 32seconds. The helix angle in the yarn layers laid down during the periodof changing traverse speed varies between 899 and 15, and is about 856through the period of relatively constant traverse speed. A conventionalribbon-breaking cycle (12% percent change in traverse speed) used duringthis period changes the helix angle by less than i0.25. The yarnpackages thus formed are identified as item C in table 1.

Packages of yarn are wound as above except that conventional variationsin the traverse rate are used. Two conditions-a normal ribbon breakingcycle (122% percent speed fluctuation in traversing) (item A), and whatrepresents an extremely large change as taught in the prior art (:10percent speed fluctuation in traversing) (item B)-are used.

Package hardness and package defects listed in table 1 were determinedby examination of 16 packages of yarn produced under each set ofconditions.

TABLE 1 Relative hardness at- Period bulge X I Z (midfans per Item Helixangle (see) (ln.) (shoulder) package) package A 8 ;lz2y 1.7 0.29 100 9219 B 8%:l:10% 4 0. 32 100 93 16 C 8%" base, +76.5% max. (to 15) 0. 16 9794 7 and ;l=2%% at base.

1 See Fig. 5 for locations of X and Z.

Z 13 see. at changing helixangle and 19 sec. at base.

varied between about 8 and about 15 (87.5 percent) and cycled at periods(A plus C, FIG. 3) of from about 5 to about 60 seconds.

As the cyclic period (A+C) is extended, ridges tend to appear on thepackage ends which, unless slight, are generally considered to beobjectionable. The time required for buildup of an objectionable ridgewill depend, of course, on several factors including yarn denier andwinding speed. Objectionable ridges appear on the package ends when theperiod of the cycle is more than about t minutes where yarndenierXWinding speed in yards per minute Relative hardness wasdetermined by comparing measurements made by a type Q Durometermanufactured by Shore Instrument Company, Jamaica N.Y., and the headrecommended by the manufacturer for use with curved surfaces. Themanufacturers instruction for the test are followed as outlinedinstructions his Bulletin R-12 and in ASTM D2240.

The packages prepared by either of the prior art methods show verysimilar package conformation and defects. It will be seen from table 1that the uniformity of the packages wound by the process embodying theinvention are greatly superior to those wound according to the prior artas indicated by a low variation in surface hardness and reduced corebulge. Shoulders are relatively softer and differ less from the hardnessat midpackage. Core bulge is reduced by a factor of about two and thenumber of spiral fans and the incidence of dip is much less. Core bulge,2a in FIG. 5 is the difference in height between the crest of the bulge2 and the innermost point of winding on the tube 1. All aspects ofpackage formation are improved. Although the changes in traverse rateand thus in helix angle of winding are extreme by prior art teaching initem B of this example, they do not provide the dispersion at thelaydown achieved by practice of the current invention.

EXAMPLE n A 70-denier l7-filament nylon yarn is wound into 7 inch longpackages weighing 6 pounds at a winding speed of 3,000 y.p.m. A basehelix angle of 9 is used throughout winding, and peak helix angles arechanged in a cycle similar to that represented in FIGS. 3, 4, period Abeing 12 seconds, period C being 18 seconds. The percentage that maximumhelix angle exceeds the base angle is plotted against the core bulgemeasured on the yarn packages. The resulting curve, FIG. 12, shows theeffect that increased helix angle change has on reducing core bulge. Atthese winding conditions this occurs above about 40 percent change.

Good packages are especially difficult to wind under high thread linetension. Generally, it is desirable to wind yarns under the lowesttension providing good continuity of winding. Bulge is accentuated whenthread line tension is increased. However, when high tension winding isnecessary, variable helix winding greatly reduces bulge and shoulders,and thus provides a unique method of achieving acceptable packageformation. Thread line tensions up to several times normal tensions maybe used.

The method of this invention has been found particularly useful in thepackaging of yarns which require winding under high tension to developand/or maintain desired yarn properties.

in practice the invention is most useful at essentially constant windingspeeds. However, the change of helix angle in winding which would occurif thread line speed were cycled, e.g., decreased for a predeterminedtime, and the cam traverse rate held constant would provide similardispersion at reversals and changing helix angles for increased packagestability i.e., a decrease in thread line speed will displace the yarnreversal inwardly of the package. Also, both thread line speed i andtraverse speed can be regulated so as to provide variable helix windingfor dispersed yarn laydown. Control of the length of yarn laydown bychanging helix angle will be dependent in part on control of thedistance between the transverse guide and the yarn laydown point.Control is simplest to maintain if this distance is kept constant.

It is also to be understood that the ribbon breaking cycle may besuperimposed on the excursions (A, FIG. 4) in helix angle. Packageswound by the method of this invention show a much more uniform packagedensity and have significantly improved appearance and a greatly reducednumber of winding defects when compared to packages wound by prior artmethods. Although surface drive windups will be commonly used in thepractice of this invention, the invention is not necessarily limited touse with these types of windups. Other changes and modifications of asimilar nature will occur to those skilled in the art without departingfrom the spirit of the present invention.

What is claimed is:

1. In a process for winding yarn into a cylindrical bodied substantiallystraight-ended yarn package wherein the yarn is wound in layers ofhelical coils at a substantially constant helix angle, including thesteps of forwarding the yarn at an essentially constant thread linespeed to the package, rotating the package at substantially constantperipheral rate of speed and traversing the yarn back and forth acrossthe package at a substantiaily constant traversal rate, the improvementof which comprises; decreasing said constant thread line speed for apredetermined time in spaced repeating periods throughout the winding ofthe package.

1. In a process for winding yarn into a cylindrical bodied substantiallystraight-ended yarn package wherein the yarn is wound in layers ofhelical coils at a substantially constant helix angle, including thesteps of forwarding the yarn at an essentially constant thread linesPeed to the package, rotating the package at substantially constantperipheral rate of speed and traversing the yarn back and forth acrossthe package at a substantially constant traversal rate, the improvementof which comprises; decreasing said constant thread line speed for apredetermined time in spaced repeating periods throughout the winding ofthe package.